LONDON -- British engineers say they have launched a "sewer war" against a giant fat blob clogging London's sewers.

A contractor employed by Thames Water to help break up a massive fatberg lodged in London's sewers is seen before descending underground to get to work, in a photo released by the utility company on Sept. 12, 2017.

Thames Water

Thames Water officials said Tuesday it is likely to take three weeks to break up the outsize fatberg lodged about 4 yards under the streets of Whitechapel, in East London.

They caution against expecting quick results as the fatberg is 250 yards long and weighs as much as 11 double-decker busses -- or about 143 tons.